Cosmological soft-graviton consistency relation
= Cosmological soft-graviton consistency relation
For a single adiabatic long tensor mode, the squeezed scalar-scalar-graviton bispectrum is the anisotropic momentum response of the scalar power spectrum:
$$
\lim_{q\to0}\frac{\langle\gamma^s_{\mathbf q}\varphi_{\mathbf k}
\varphi_{-\mathbf k-\mathbf q}\rangle'}{P_\gamma(q)}
=-\frac12\epsilon_{ij}^s k_i\partial_{k_j}P_\varphi(k).
$$